Vibratory impact bender

ABSTRACT

This invention relates to the technique for the bending fabrication of an elongated hollow bar stock having an open slot extending over the whole length thereof by means of a first and a second rotary die element cooperating with each other into a hollow bend. The invention is characterized by a vibration-generating means and a vibration-transmitting means from said generating means to the second die element for providing a continuously repeated percussion effect upon the bar stock, as the bending process progresses.

nited States Patent Hikida et a1. [45] Aug. 15, 1972 15 1 VIBRATORY IMPACT BENDER [5 References Cited [72] Inventors: Ryotaro Hikida, 50, l-chome, UNITED STATES PATENTS Nagoya; 3,473,361 10/1969 Cwik ..72/150 Talklch} 4 Otokoyama, 2,996,100 8/1961 Newhall ..72/369 Narprrn-cho, MldOfl-kfl, N g y 2,465,101 3/1949 Johnson ..72/ 150 Jumchlm h 2,841,201 7/1958 Cheatle ..72/141 Filed:

Kashiwagi-cho, Mizuho-ku, Nagoya;

Atsushi Danno, 2-20, Hitotsuyama;

Masao Matsui, 13, 2-chome, Hisakata, both of Showa-ku, Nagoya; Mitigi lnaba; Mit'uyuki lsogai, 'both of c/o Aisin Seiki Kabushiki Kaisha, 1 Asahi-machi 2- chome, Kariya, all of Japan.

June 18, 1970 Appl. N0.: 47,473

U.S. Cl ..72/ 150, 72/369 Int. Cl. ..B2ld 9/05 Field of Search ..72/150, 141, 369

Primary Examiner-Charles W. Lanham Assistant Examiner-R. M. Rogers Att0rney--Sughrue, Rothwell, Mion, Zinn & Macpeak ABSTRACT This invention relates to the technique for the bending fabrication of an elongated hollow bar stock having an open slot extending over the whole length thereof by means of a first and a second rotary die element cooperating with each other into a hollow bend.

The invention is characterized by a vibration-generating means and a vibration-transmitting means from said generating means to the second die element for providing a continuously repeated percussion effect upon the bar stock, as the bending process progresses.

6 Claims, 12 Drawing Figures PATENTEDAuc 15 I972 SHEET 1 BF 3 FIG. 2

FIG. 8

VIBRATORY IMPACT BENDER This invention relates to the technique for the bending fabrication of an elongated hollow bar stock having an open slot extending over the whole length thereof by means of a first and a second rotary die element cooperating with each other into ahollow bend.

The bending process may be performed with the opening slot of the hollow bar stock directing laterally or alternatively radially of the finished bend, the bend ing operation being naturally performed in the plastic range of the material of the stock.

It has been already disclosed in the specification of our pending Japanese Pat. Application No. 23746/ 1967 to perform a bending formation of a bend from a hollow bar stock of the above kind having a C- or U-cross-section with its open slot directing outwardly or inwardly of the bend, as the case may be, in-v deed, by applying the stock continuously with a series of vibratory impacts at the bending spot of the stock.

In this prior improved technique, one of the shapers or die elements is introduced through the open slot into the hollow space of the stock, while the other die element is placed in opposition to the first die element through the intermediary of the web of the stock, the vibratory percussion being applied under these conditions to the stock through one of the die elements. When relying upon this improved technique, the bending fabrication must be limited to certain specific application possibilities. When it is desired to process variously shaped hollow bar stocks especially having such a cross-sectional configuration that the shaping tool or die element can not be inserted from outside into the hollow core, the aforementioned improved technique can not be relied upon. An elongated hollow bend the open slot of which is opening laterally of the bend also I can not be fabricated.

It is a main object of the invention to provide a process for the manufacture of elongated hollow bends without formation of wrinkles, rises or the like defects thereon from correspondingly prefabricated bar stocks.

A further object is to provide a process of the above kind, which is applicable to a more various variety of the hollow cross-sectional configuration of the bar stock.

It is still further object of the present invention to provide a bending process of the above kind for the manufacture of more precisely dimensioned hollow bends than hitherto attainable.

A further object is to provide a machine adapted for performing the process according to this invention without encountering the aforementioned various drawbacks.

In carrying out the conventional bending process for the manufacture of an elongated hollow bend having an open slot extending over the whole length thereof, a core made of low melting metal, hard rubber or the like is fixedly inserted into the hollow space of the bar stock in advance of the bending operation and then the bending force is applied to the stock laterally thereof so as not to pass through the opening slot of the stock. In practice, however, the insertion and disengaging operations for the core into and from the hollow space of the stock, respectively, are highly troublesome and difficult to execute, in addition to the defective and unsatisfac tory dimensional and configurational preciseness of the products. In order to avoid these defects, the bend had to be manufactured through a longitudinal welding process of partially shaped elements into one piece. This kind of manufacturing technique can be practised only with an unallowably low fabrication efficiency.

These and further objects, features and advantages of the invention will become more apparent when read the following detailed description of the invention by reference to the accompanying drawings, in which:

FIG. 1 is a schematic front view of an embodiment of the machine adapted for carrying out the process according to this invention, wherein, however, several parts have been at least partially sectioned for demonstrating inner working parts.

FIG. 2 is a perspective view of a second embodiment of the machine of the above kind.

FIG. 3 is a plan view of the second embodiment of the machine.

FIG. 4 is a sectional side view of the machine shown in FIGS. 2 and 3, wherein, however, several parts have been sectioned.

FIG. 5 is an enlarged detail view of a part of the machine which is shown in a horizontal rectangular dotted line block E shown in FIG. 3.

FIG. 6 is an enlarged detail view of a part of FIG. 3 which is encircled by a dotted line block F shown therein.

FIG. 7 is a sectional view taken substantially along a section line VII-VH shown in FIG. 6.

FIG. 8 is a perspective view of a modified design and arrangement of the assembly of an anvil and its support which plays an important role in practice of the inventron.

FIG. 9 is a perspective of a modified anvil and its related several parts.

FIG. 10 is a view of essential parts of a modified machine from the embodiment shown in FIGS. 25.

FIG. 11 is an enlarged view of a part of FIG. 10 which is encircled by a rectangular dotted line block G shown therein.

FIG. 12 is a cross-sectional view substantially taken along a section line XII-XII shown in FIG. 10.

Referring now to the accompanying drawings, several preferred embodiments of the invention will be described in detail.

In FIG. 1, an apparatus for shaping a C- or U-sec tioned and elongated stock into a longitudinally areshaped bend is shown in its schematic elevation, of which a first die element 10 is formed into a rotatable disc having its shaft 11 supported through proper bearing means by a machine frame omitted from the drawing for simplicity thereof.

This die element 10 is formed on its peripheral surface with a die proper 12 which is formed into a circular and peripheral flange having a recess of such cross sectional configuration corresponding substantially a part of that of the working stock 16. (See also FIG. 12) This stock 16 is shown only schematically by chaindotted lines.

Numeral 14 represents a gripper which is fixedly mounted on die element 10 and fitted at its outer end with a chuck 15 adapted for gripping firmly, yet detachably one end ofthe bar stock 16 to be fabricated into a bend.

There is provided a further chuck 17 which is attached to the inner end of a hydraulic tension device 18 comprising a hydraulic piston-and-cylinder unit which has a similar design and function of a device 35 to be described. Numerals 40 and 41 represent inlet and outlet pipings connected with a certain hydraulic pressure source, not shown, for supplying fluid under pressure to and discharging it from the device 18, respectively. The chuck 17 is adapted for gripping the opposite or lower end of the bar stock 16. The chuck 17 may have a construction similar to that shown in FIG. 5.

Core assembly, generally shown at 42, comprises an anvil 42a having a cross-sectional configuration substantially corresponding to that of the inside open space of the stock 16, a support bar 42b and a fixture 42c adjustably fixing one end of bar 42b. Details of anvil 420 may be well supposed from FIG. 6.

Core assembly 42 carrying thereon the stock 16 in the form of a kind of sheath is positioned as shown at a level corresponding to that of die proper 12 when seen by a viewer upon FIG. 1 so that the anvil 42a can act as the reaction member during the bending fabrication stroke to be described.

Now assuming that the hollow bar stock 16 is positioned in a tangential contact with the die proper 12 on die element and both ends of the stock 16 are caught by respective chucks and 17, and the die element is caused forcibly to rotate about its shaft 11 in counter clockwise direction in FIG. 1, with the tension device 18 hydraulically energized, so as to provide a proper tensile force to the stock.

It may be supposed that in this way the stock may be well transformed into a bend with the open slot thereof directing laterally by subjecting the stock to the bending and tensile'stresses during the turning stroke of the die element 10 amounting to about 180 during which the gripper 14 moves around from its full line position I to its chain-dotted line one shown in FIG. 1.

During this semi-circular bend fabrication stroke, the tension device 18 is moved a distance which corresponds to the peripheral and semi-circular shift of the die element 10, while the core 42 is kept stationary. In practice, however, appreciable wrinkles and rises will frequently be formed on the inner and outer peripheral surfaces, in addition to the collapsing deformations of the stock. A disadvantageous spring-back phenomenon will frequently be encountered when the chucking grip of the both ends of the stock at 15 and 17 is released, by virtue of its elasticity in the longitudinal direction, thereby a deformation from the desired final shape being invited when seen in the same direction. These various drawbacks disturbing the realization of the final and fabricational dimensions to an appreciable degree can be substantially obviated when relying upon the novel teachings of the present invention, as will become more apparent as the description proceeds. If necessary, the slot opening of the bar stock may be directed radially in place of laterally.

In the inventive machine shown in FIG. 1, there is provided second die element acting as a striking member which is formed into a rotatable disc having on its peripheral surface a kind of circular flange serving as the shaper per se. This shaper flange 19 has an inner cross-sectional configuration corresponding to a substantial part of the remaining cross-sectional outer configuration of the bar stock 16.

The wheel like die element 20 has a shaft 21 which is rotatably supported on an elongated slide 22 arranged slidable in a slot 24 formed in a support member 23 and along a straight line connecting the axes of the shafts 11 and 21.

Across the slot 24 at a proper position in proximity of the right-hand end thereof, a stop member 25 is provided, a compression spring 26 being inserted between the slide 22 and the stop 25 for resiliently urging the former to move leftwards.

A rotatable hub 27 is mounted on slide 22, an eccentric weight mass 29 being fixedly mounted on the hub 27. Pulley 30 is also fixedly mounted on the same hub and mechanically connected through a belt 32 with a further pulley 31. This pulley 31 is fixedly mounted on a shaft 43 which is rotatably mounted in turn by a pedestal 44 rigidly supported on the support member 23.

The pulley 31 is driven through a belt 45, only schematically shown, by an electric drive motor 33 which is fixedly mounted on the same member 23.

When the motor 33, the electric wiring thereof being omitted from the drawing only for simplicity, is energized to rotate, with the related parts positioned as shown by respective full lines, motion is transmitted therefrom through belt 45, pulley 31, belt 32 and pulley 30 to the hub 27, thereby the eccentric mass 29 being brought into a continuous rotation and vibratory motion being applied onto the slide 22 by means of a shaft 28 to a degree which is determined by the weight of mass 29, the eccentricity and revolutions thereof. Since the movability of slide 22 in the longitudinal direction thereof is limited by the guide slot 24, the thus generated vibratory movements of the slide is performed in the said direction only. On account of this vibratory movement of slide 22, and by the provision of the urging spring 26 for said. slide, the second die element 20 will collide against the first die element 10 and then recede therefrom in a repeated manner, the frequency of this attacking and receding movement of the member 20 being same as that of said vibratory movement. Hereinafter, this attacking movement of the member 20 against the bar stock is referred to as vibratory impact.

In'this way, the hollow bar stock 16 is subjected to a repeated cycle of impactly shaping action exerted by the die element 20 at the position wherein a part of the shaper flange 12, anvil 42a and a part of the shaper flange 19 on the member 20 exist substantially in a common horizontal plane and at the initial bending zone for the bar stock.

As was briefly hinted in the foregoing, the bending action is applied onto the hollow bar stock of C- or U- section with use of the present machine shown in FIG. 1. In this case, the outermost layer of material of the stock will naturally be subjected to a maximum degree of tensile plastic deformation in the peripheral direction of the bend while the innermost material layer of the stock having a minimum curvature will be subjected to a minimum tensile stress or even a compressive stress, thereby material wrinkles being more frequently invited in the latter than the former. It is therefore preferable to apply the vibratory impacts by the die element 20 upon the larger radius portions of the stock and along the periphery thereof as the stock 16 moves around during whole of the bending stroke,

so as to provide tensile hammering effect upon outer material portions. I

As shown in FIG. 1, support member 23 has a longitudinal extension 34 extending from the inner end edge of the member being positioned in proximity of the shaft 21 of second die element 20, said extension being pivotably and concentrically mounted with the shaft 11.

Hydraulic piston-and-cylinder unit 35 comprises piston rod 36 which is linked with the outer end part of support member 23 through a bell crank lever 38 and a connecting link 39, said lever being pivotable around a pivot pin'37 studded on the machine frame, not shown. With this arrangement, an application of fluid under pressure through inlet piping 46 to piston chamber 35a of the unit 35 will move the piston rod 36 leftwards and upwards in FIG. 1 and motion is transmitted through bell crank 38 and connection rod 39'to the support member 23 which is thus pivoted from its full line position to its chain-dotted line position and within a certain pivoting angle alpha. By this operation selected to a certain or other degree, the second die element 20 may be shifted, as desired, in its contacting point with the' die proper 12 which means that the vibratingly impacting point of the die element 20 against the bar stock 16 may be varied as occasion will desire and along the shaper flange 12.

When it is desired to shift the impacting point by the striking member 20 within the angularly adjustable range alpha, the support member 23 is positioned beforehand at its full line position or its null position, in advance of the grip of the bar stock by the chucks l5 and 17. Then, the stock is gripped at its ends by these chucks and the support member 23 is angularly adjusted in the manner as was referred to hereinbefore. Under these adjusted and ready-for-operating position of the related working parts, the eccentric mass 29 is brought into rotation, as was described in the foregoing, so as to initiate the vibratory impacting operation, while at the same time the first shaping die is brought into rotation. In this case, the core assembly 42 is kept stationary. Unloading of the fabricated bend or attachment of a new bar stock may be performed upon receding the second die element against the spring force at 26 to the initial position.

In FIGS. 2-4, a second embodiment of the invention is more specifically shown.

Numeral 101 denotes a die element which is fixedly mounted on a turn table 102 mounted in turn rotatably on a stationary machine frame A. On the peripheral surface of the die element 101, there is provided a shaping flange 103. A bar stock 107 to be subjected to a bending job is kept under tension by being gripped at its both extremities by chucking means 106 mounted on the turn table 102 and a further chuck 108 of a tension device 109 mounted on the machine frame A.

The apparatus adapted for application of vibratory impacts upon the bar stock 107 comprises a disc 118 on which an eccentric mass 120 is fixedly mounted, said disc 118 having a shaft 119 which is rotatably mounted on the support frame 113. This frame 113 is fixedly attached with a second die element 111 at an opposing position to the first die element 101, said frame being mounted in turn at the top ends of a pair of plate springs 117 which are arranged at a certain distance from each other and in parallel to each other, while the lower ends of these plate springs are attached fixedly to a support base 114 which mounts fixedly an electric drive motor 124. Motor 124 has a pulley 122 fixedly mounted on the motor shaft 124a as shown and drivingly connected with a further pulley 121 fixedly mounted on the disc 118 through the intermediary of a belt 123.

When the motor 124 is started, the eccentric mass is thus brought into rotation, thereby the support frame 113 performing a vibratory movement, as in the case of the first embodiment, or more specifically in the plane of the drawing paper when seen in FIG. 4.

On account of the resilient mount of the support frame 113 through plate springs 117 on the support base 114, an oscillation of the frame in the longitudinal direction of the plate springs 117 is naturally checked effectively, while the vibration of the frame when seen in the lateral direction of these springs for deflecting the latter is generated and maintained. In this way, the die element 111 will apply vibratory impacts upon the bar stock 107 at its part which is placed between the both die elements through the anvil shown by the same reference number 42a in FIG. 4 as before.

Freely rotatable wheels 131 are attached to the bottom surface of the support base 114 which wheels are adapted for rolling on the upper surface of machine frame A.

A hydraulic pusher device 133 (FIGS. 2 and 3) is pivotably mounted at 132 on the machine frame A; said device is provided with a piston rod 134 which is connected at its free end through a joint 135 with the support base 114.

The machine frame A is formed with a stop shoulder 136 in proximity of the front part of the turn table 102. When the support base 114 is advanced through piston rod 134 and by actuation of hydraulic pusher 133, the base will be brought into abutment with the stop shoulder, thereby unintentional fluctiative positioning of base 114 caused by the effective vibration being positively prevented.

By pivoting the pusher device 133 around its pivot 132 as occasion may desire, the support base 114 may be shifted correspondingly along stop shoulder 136 a certain distance corresponding to the angular adjusting range beta relative to the turn table 102, as in the similar way referred to above in connection with FIG. 1.

The provision of said stop shoulder 136 serves for assuring the desirous correct engagement of the second die element 111 against the shaping flange 103 on the die element even upon displacement of the support base 114. Joint 135 allows the necessary relative pivotal movement between piston rod 134 and support base 114.

It must be positively prevented to unintentionally recede the support base 114 from the die element 101 to be caused by the vibration transmitted from the rotating eccentic mass 120 to the said base. There must be further provided certain means for absorbing the reaction force to the impacts applied by the die element 111 upon the bar stock 107. In order to meet these requirements, it suffices to supply fluid under pressure of a predetermined value to the hydraulic pusher device even during the vibratory impacting period.

As seen from FIG. 4, a gripper pawl 137 is provided which is pivotably mounted in machine frame A in such a way that it is not exposed normally above the upper surface of the frame so that it is kept normally in its hidden state. This pawl is made integral with a segmental gear 138 which meshes permanently with a gear 139. By rotating the latter manually, although the manipulating means have been omitted only for simplicity and except its shaft fixedly mounting the gear, the pawl erected above the upper surface of the machine frame and brought into pressure engagement with the joint 135, so as to hold the support base 114 in abutment against the stop shoulder 136 in a positive way. With this arrangement when employed, fluid under pressure may be discharged from inside of the hydraulic pusher device 133.

The operation of the second embodiment so far shown and described is as follows:

The hollow metallic bar stock to be fabricated into a bend and with its open slot directing downwards (FIG. 4) is placed in tangential contact with the shaper flange 103 of die element 101 and the both ends of the bar stock are gripped by chucks 106 and 108, respectively. Core assembly 42 comprises a supporting bar 42b which is fixed to the fixture 420 on base frame A, said supporting bar being inserted in the hollow core of the bar stock. The anvil 42a formed on one end of the supporting bar is placed between the first and second die elements. Support base 114 is kept in its rearwardly receded position by the piston rod 134 by actuation of the hydraulic pusher device 133. Upon the bar stock is gripped by chucks in the aforementioned way, the turn table 102 is rotated slightly if it is necessary and then fluid under pressure is supplied to the device 133, so as to expand the piston rod 134 for bringing the support base 114 into abutting engagement with the stop 136, while the hydraulic pressure prevailing in the cylinder of the device 133 is kept in force.

The shaper flange 110 of die element 111 supported by plate springs 117 on the support base 114 is kept in contact with a medium pressure exerted by said springs 117 and at the point where the bar stock 107 is kept in tangential contact with the shaper flange 103.

When motor 124 is started, motion is transmitted therefrom through belt 123 to the disc 1 18, thereby the eccentric mass 120 being rotated. Therefore, support frame 113 performs repeated collision and repulsion against and from the bar stock 107 through the anvil 42a under the influence of the elasticity owned by the plate springs 1 17. In this way, such number of vibratory impacts that correspond to the number of rotation of the mass are applied to the bar stock.

When turn table 102 is rotated under these operating conditions, the bar stock 107 is subjected to a bending action in a horizontal plane with its opening slot directing downwards thereof, while the stock is applied with tension by the device 109. The main bending force, in this case, is exerted by the shaper flange 103 of die element 101. At the same time, a series of vibratory impacts are applied to the bar stock which is supported by the anvil 42a inserted in the hollow core of the latter. In this way, a satisfactory bending formation of the stock is realized within the plastic range of the stock material and without formation of wrinkles and the like defective workmanships. In this case, the device 133 can be pivoted around its pivot 132 within a certain angular range denoted by beta corresponding to that shown by the same reference symbol in FIG. 1, so as to select a proper impacting point concerning the die element 111. Under normal operating conditions, however, the angle beta may preferably be set to almost null in the present embodiment.

After completion of the bending job, a notch, not shown, formed on the turn table 102 at a certain and properly selected point, will cooperate with a limit switch 140, so as to control the oil supply and discharge to and from the pusher device 133 for contracting the piston rod 134, although the electric and hydraulic control means serving for this purpose have been omitted from the drawing only for their very popularity. In this way, die element 111 is receded to its nonworking position for release of chucks 106 and 108. Then, the finished bend is unloaded from the machine; and the device 109 and turn table 102 are returned to their original position for assuming a ready-for position for the next bending job.

FIG. 5 represents an enlarged and more specific detail view of a part of FIG. 3 which has been encircled by a dotted rectangular frame E. This figure represents a sectional view of the fixture 420 for supporting bar and the chuck 108 adapted for gripping one end of bar stock 107. The anvil 42a is inserted into the hollow core of bar stock 107 (see, also FIG. 3) and the opposite end of anvil support bar 42b is passed through a bore 61 formed substantially at the center of the chuck 108 and fixed in the fixture 420.

The opposite end of supporting bar 42b is formed with adjusting screw 50 comprising a left-hand screw part 50a and a right-hand screw part 50b, an adjusting member 53 being mounted at its intermediate point, so as to form a turn buckle.

By turning the adjuster 53, the position of anvil 42a fixed on the tip end of the bar 42b can be adjustingly modified in its longitudinal direction. Chuck 108 is formed with a bore 61 for reception of anvil supporting bar 42b. The bar stock 107 is gripped in a hydraulically operated way between inner jaw 62 and outer jaw 63. Chuck 108 is connected with a pair of a parallel plates 64, the opposite ends thereof being connected with tension device 109. By this arrangement, the bar stock 107 is subjected to a properly selected tension. In addition, chuck 108 is arranged shiftable in the longitudinal direction of the bar stock.

FIG. 6 is an enlarged detail view of a part of FIG. 3 which has been encircled by a block F shown the rein. The bar stock 107 is positioned between shaper flanges 103 and 110 of the die element 111 through anvil 42a and subjected to vibratory impacts exerted by the die element during the bending fabrication. FIG. 7 represents a section taken along a line VIIVII shown in FIG. 6.

The shaping flange 103 of die element 101 has an inside diameter Rl which corresponds to the desired inside bending radius, equally shown by the same reference symbol, for the bar stock 107 and the crosssectional configuration of said flange 103 when seen in its inside part consists of substantially a half of the outside configuration of cross-section of the bar stock, as most clearly be seen from FIG. 7.

In the range of the arc-shaped part a-b of the shaping flange 103 shown in FIG. 6, it is kept in tight contact with the stock 107. The arc-shaped part e-m of anvil 42a has a radius R2 which corresponds substantially to the desired outside diameter of the corresponding part of the finished bend, while the straight line parts j-k and m-n are kept in parallel to the supporting bar 42b. The point m represents that part where repeated impulses are applied from the die element to the bar stock. As seen from FIG. 7, the anvil 42a has been inserted into the hollow core of the bar stock.

The shaping surface 110 of second die element 1 l 1 is convexedly curved for the convenience of impacts application. At a point c on the shaping surface 1 which is positioned in opposition to said point m on the anvil, it represents in its cross-section substantially the remaining part of the bar stock section and so designed and arranged substantially to enclose from outside the said remaining half of the bar stock section.

Turn table 102 is fitted with a chuck 106 which is similar to that shown at 108 in FIG. 5. This chuck 106 is adapted for gripping another end of the bar stock 107, as was referred to hereinbefore.

With rotational movement of turn table 102, the chuck 108 is shifted in the longitudinal direction thereof and thus the impacting point of the die element 111 relative to the work piece 107 will thereby be varied. During the bending fabrication stroke, the anvil 42a does not follow after the axial movement of the piece 107, as was referred to hereinbefore.

A considerable part of the vibratory impact force applied from the die element is received by the elastic support bar 42b and thus a destructive influence upon the anvil and the support bar can be effectively avoided.

FIG. 8 shows a modification of the supporting means for support of the anvil on the base frame. In this embodiment, anvil 42a is fixedly mounted on a mount 70 which is mounted in turn on a bracket 73. The mount 70 is coupled with the bracket 73 through a tongueand-groove connection as seen. The anvil employed in the present embodiment has substantially similar general configuration as that shown in FIG. 6.

The anvil mount 70 has generally a kind of male configuration and its upper part 71 is fixedly attached to anvil 42a and its lower flat portion 72 is coupled with bracket 73, as was referred to hereinbefore. The mount 70 is slidable in the bracket 73 and in the direction of the vibratory movement of the die element 111, thereby the shocks due to vibration being prevented from being transmitted to the bracket 73 which has generally a L-configuration and formed at its lower flat portion with a pair of elongated openings 74 extending in series in the perpendicular direction to the vibratory movement of the die element 111.

The bracket 73 is so designed and arranged that it allows a shift of anvil 42a relative to the die element 111 and in the lengthwise direction of the bar stock 107 so as to occupy an optimum relative position. At this position, when attained bolts are passed through said openings 74 for fixingly mounting the bracket onto the machine frame A, as in the similar way as referred to hereinbefore by consultation with FIGS. 24.

FIG. 9 shows a modified form of the anvil. The modified anvil is shown at 42a, while other parts shown 7 are substantially same as shown in FIG. 8. The anvil 42a has its circular plan configuration and its cross-section taken on a lateral plane passing through its axis corresponds to the section of hollow core of the bar stock.

In FIG. 10-12, a further modified design of the machine for the preparation of elongated hollow bends is substantially shown.

The hollow bar stock is shown at 107 as before.

According to our practical experiments, a collapsing deformation may be encountered even with use of the foregoing embodiment machine by virtue of delicate nature of the stock material and of smaller radius of bending. This kind of collapsing deformation is shown by a thick small arrow in FIG. 12, indeed, in its forming direction only. With use of the machine built in accordance with the present modification, however, the invitation of such collapsing can positively be avoided.

In the present machine which is shown only of its main working parts only for simplicity, there is provided a shaping band or strip which is inserted between anvil 42a and bar stock 110. For convenience of this modified arrangement, the chuck 108 is formed with a corresponding flat opening to the cross-section of the strip 75, although not specifically shown. Other construction of the present modification is similar to structure shown in FIGS. 3, 5 and 6.

FIG. 11 is an enlarged view of a part at G in FIG. 10 and thus the structure and function thereof are selfexplanatory.

As may be well supposed from FIG. 12, the shaping strip 75 comprises a thin band element made of spring steel or the like material and is inserted into the hollow core of the bar stock 107 and between the inside or bottom surface of anvil 42a and the inside or lower flange of the U-sectioned bar stock 107. One end of the strip 75 is gripped together with the corresponding end of bar stock 107 by the chuck 106. At the working position for the bar stock where the latter is subjected to repeated or vibratory impacts, as shown in FIG. 12, the inner hollow space of the stock is filled with anvil 42a and auxiliary shaping strip 75 practically without no idle gap. The opposite end of the shaping strip 75 is gripped by a chuck 76 of the tension device 77 through a bore 64 formed in the chuck 108. With the tension device 77 actuated, the shaping strip 75 is properly tensioned, and then the second die element 11 1 is brought into operation for applying repeated or vibratory impacts as before to the bar stock 107 fitted with anvil 42a and shaping strip 75 and supported on the rotating first die element 101 acting as a shaper and reactioner.

During this percussingly shaping stroke, the inside peripheral surface of bar stock 107 is kept in abutting and pressure contact with the shaping part 103 of the first die element 101, thereby the otherwise appearing collapsing tendency of the stock under fabrication being perfectly prevented and an optimum fabrication preciseness being assured.

When a bar stock of soft metal such as aluminium is being processed, the use of the shaping strip will result in a considerably reduced tension applied to the stock, even substantially to nil under extreme conditions.

The effect of the shaping strip results in an effective action against a possible separation of the bar stock from the shaping part of the first die element 101 by binding the stock to the desirous working position, thereby preventing otherwise frequently encountered formation of wrinkles by applying the stock with counter-acting compressive stresses especially in the longitudinal direction of the stock.

It will thus be seen from the foregoing that in the practice of the inventive process, an elongated hollow bar stock prefabricated into a standard cross-sectional configuration is placed so as to contact with the shaping pan of a first die element of rotary type, the crosssection of said shaping part of the die element representing a part of the cross-section of the product bend, one end of the bar stock is fixed on said die element, while the opposite end of the same is gripped by a tension device for keeping the work stock in a tensioned state, an anvil is positioned within the interior hollow space of the stock, said anvil having its crosssection corresponding to that of the hollow space of the stock, a second die element is positioned in opposition to said first die element at the position where the anvil is situated, said second die element being brought into oscillation towards and from said first die element, the oscillation being transmitted thereto from a vibrationgenerator, preferably of the eccentric mass type, said tension device being moved in synchronism with the rotary movement of said first die element, thereby repeated percussive impulses being applied to the stock, as the stock passes through the working point substantially lying on an imaginary plane connecting the opposing die elements through said anvil. Under extreme case, however, said anvil can be obviated if the material of the bar stock is considerably tough.

Although in the foregoing, the vibration-generator is of the eccentric mass type, it can be replaced, when necessary by a hydraulic piston-and-cylinder type, or even by an electro-magnetically operated plunger type vibration-generator, as may well be supposed by any person skilled in the art. Spring type vibration-generator can also be utilized when occasion will so desire.

The vibratory impacts applied from the second die element onto the bar stock varies in their strength within a broad range from such a degree that the second die element or rotary percussion tool is kept in light pressure contact with the bar stock by a spring force, so as to provide a vibratory movement added with said spring force, thus creating a resultant force acting as an oscillative impact, to such a strong degree that the oscillative impacts will provide per se a sufficient plastic deformation in the material of the stock.

According to our practical experiments, it has been found that without application of the oscillative impacts, the bar stock must be applied with a substantial tension exerted by the tension device during the whole bending stroke, in addition to the regular bending effort exerted by the rotary movement of the first die element, as well as the shift of the stock-gripper means, especially when the bending stresses are to be of considerable values. With the application of said kind of vibratory impacts from the second die element to the bar stock, the aforementioned tension may be of substantially minor value which will amount to substantially nil under extreme conditions.

We have made experiments with use of the apparatus shown in FIG. 1, but depleting of the tension device, and found that the desirous formation of bends can be realized without application of the tension to the bar stock. In addition, it has been found that the use of the shaping strip as at will assist substantially the realization of an ideal process for the manufacture of hollow bends. The results are shown in the following Table.

It should be stressed at this stage that the application of vibratory impacts onto the stockdoes not aim at the vibration per se, but it concerns definitely the invitation of material shifts in the work piece by the oscillatingly applied mechanical impacts or percussions. It has been found that an application of high frequency ultrasonic energy, as an example, does not always provide the desirous effect.

With use of the embodiment machines, the revolutions per second of the eccentric mass will amount to 5-60 with superior results. This means the vibration of the transmitting means varies from 5 to 60 cycles per second, i.e., the frequency of application of impacts varies from 5 to 60 times per second. With a lower frequency than above specified, the percussion effort must be selected to a substantial value. For satisfying this requirement, the vibration-generator must be substantially large in its performance or capacity to such a degree that it can not be adopted from economical reason. With heavier vibratory impacts, the stock may become defective by the percussive impressions formed on the stock by the second die element.

The embodiments of the invention in which an exclusive property or privilege is claimed are as follows:

1. An apparatus for bending an elongated hollow bar stock having an open slot extending over the whole length thereof comprising:

a base frame,

a first die element rotatably mounted on said base frame, said first die element having a portion adapted to be in direct contact with the stock,

a second die element having a portion adapted to be in direct tangential contact with the stock,

an anvil inserted within the hollow space of said stock and positioned between said first and second die elements, and means for supporting said anvil,

first gripping means provided on said first die element for rotation with said first die element for gripping one end of said stock,

second gripping means mounted on said base frame for gripping the other end of said stock, and

means connected to said second die element for reciprocating said second die element toward and from said first die element 5 60 times per second to apply the same number of impact forces onto said stock to be contacted with said second die element, said means including:

means for generating mechanical vibrations of 560 cycles per second,

means for transmitting said vibrations to said second die element, said means being provided between said vibration generating means and said second die element,

a supporting member for supporting said transmitting means, and

spring means inserted between said transmitting means and said supporting member, said spring means being adapted to resiliently urge said transmitting means toward and from said second die element, whereby impact forces of 60 times per second added with a spring force are applied to the outside of the bend of the stock.

2. An apparatus according to claim 1, wherein said second die element is a rotatable disc, said vibration generating means comprises a rotatable eccentric mass and a motor for rotating said mass, and said vibration transmitting means is a slide arranged on a plane including the centers of said first and second die elements.

3. An apparatus according to claim 1, wherein said vibration generating means comprises a rotatable eccentric mass and a motor for rotating said mass, said vibration transmitting means is a frame, and said spring means is a pair of plate springs, said frame being mounted at the top ends of said plate springs and fixedly attached to said second die element, said plate springs being in turn fixedly mounted on a support base.

4. An apparatus according to claim 1, further comprising a shaping strip inserted between said anvil and said stock, the ends of said shaping strip being gripped by said first gripping means and a third gripping means adjacent thereto, whereby said stock is kept in abutting and pressure contact with said first die element.

5. A method of bending an elongated hollow bar stock having an open slot extending over the whole length thereof in an apparatus having first and second die elements, an anvil and means for applying impact forces to the stock, comprising:

inserting an anvil into the hollow space of said stock so as to be positioned between said first and second die elements,

gripping both ends of the stock by gripping means,

forcibly passing the stock between said first and second die elements by rotating said first die element, and

colliding said second die element against the stock 5-60 times per second for applying the same number of impact forces to the outside of bend of the stock by said second die element during the bending operation.

6. A method according to claim 5 further comprising, after the step of inserting said anvil, inserting a shaping strip between said anvil and said stock. 

1. An apparatus for bending an elongated hollow bar stock having an open slot extending over the whole length thereof comprising: a base frame, a first die element rotatably mounted on said base frame, said first die element having a portion adapted to be in direct contact with the stock, a second die element having a portion adapted to be in direct tangential contact with the stock, an anvil inserted within the hollow space of said stock and positioned between said first and second die elements, and means for supporting said anvil, first gripping means provided on said first die element for rotation with said first die element for gripping one end of said stock, second gripping means mounted on said base frame for gripping the other end of said stock, and means connected to said second die element for reciprocating said second die element toward and from said first die element 5 - 60 times per second to apply the same number of impact forces onto said stock to be contacted with said second die element, said means including: means for generating mechanical vibrations of 5-60 cycles per second, means for transmitting said vibrations to said second die element, said means being provided between said vibration generating means and said second die element, a supporting member for supporting said transmitting means, and spring means inserted between said transmitting means and said supporting member, said spring means being adapted to resiliently urge said transmitting means toward and from said second die element, whereby impact forces of 5-60 times per second added with a spring force are applied to the outside of the bend of the stock.
 2. An apparatus according to claim 1, wherein said second die element is a rotatable disc, said vibration generating means comprises a rotatable eccentric mass and a motor for rotating said mass, and said vibration transmitting means is a slide arranged on a plane including the centers of said first and second die elements.
 3. An apparatus according to claim 1, wherein said vibration generating means comprises a rotatable eccentric mass and a motor for rotating said mass, said vibration transmitting means is a frame, and said spring means is a pair of plate springs, said frame being mounted at the top ends of said plate springs and fixedly attached to said second die element, said plate springs being in turn fixedly mounted on a support base.
 4. An apparatus according to claim 1, further comprising a shaping strip inserted between said anvil and said stock, the ends of said shaping strip being gripped by said first gripping means and a third gripping means adjacent thereto, whereby said stock is kept in Abutting and pressure contact with said first die element.
 5. A method of bending an elongated hollow bar stock having an open slot extending over the whole length thereof in an apparatus having first and second die elements, an anvil and means for applying impact forces to the stock, comprising: inserting an anvil into the hollow space of said stock so as to be positioned between said first and second die elements, gripping both ends of the stock by gripping means, forcibly passing the stock between said first and second die elements by rotating said first die element, and colliding said second die element against the stock 5-60 times per second for applying the same number of impact forces to the outside of bend of the stock by said second die element during the bending operation.
 6. A method according to claim 5 further comprising, after the step of inserting said anvil, inserting a shaping strip between said anvil and said stock. 